The water on the surface of the earth escaped from the interior of the earth, and after about 3.5 billion years of accumulation and evolution, it gradually formed today's hydrosphere. The formation of hydrosphere not only changed the face of lithosphere, made the phenomena in the atmosphere complicated and diverse, but also led to the emergence of biosphere. Therefore, the emergence of water and the formation of hydrosphere are the most important events in the natural history of the earth.
The research field of hydrology is very extensive. From the water in the atmosphere to the water in the ocean, from the water on the land surface to the groundwater, it is the research object of hydrological science; The relationship among hydrosphere, atmosphere, lithosphere and biosphere is also the research field of hydrology. Hydrological science not only studies water quantity, but also water quality, not only studies the instantaneous dynamics of current water regime, but also explores the life history of global water and predicts its future changing trend.
Although the amount of water on land accounts for only about 3.5% of the global total, almost all fresh water is distributed on land. The whole human beings live on land, and the most complicated hydrological process also occurs on land, so the research on land water is especially valued by people. Soil and water literature is the main part of hydrological science. Hydrological knowledge in ocean and atmosphere has been classified as oceanography and atmospheric science respectively.
The research object of hydrology
There are about 65.438+0.39 billion cubic kilometers of water on the earth, which are distributed in the ground, underground and atmosphere in liquid, solid and gaseous state, forming rivers, lakes, swamps, oceans, glaciers, snow, groundwater and atmospheric water, forming a vast hydrosphere. The hydrosphere is in an endless state of motion, and all kinds of water bodies in the hydrosphere are closely related, transformed and constantly updated through hydrological processes such as evaporation, water vapor transport, precipitation, surface runoff and underground runoff, forming a huge dynamic system.
In this system, seawater evaporates into water vapor under solar radiation, rises into the atmosphere, and is carried over the land by airflow. Under certain weather conditions, precipitation falls to the ground. Part of the falling water evaporates back into the atmosphere, and the other part forms surface runoff along the ground or seeps into the ground to form underground runoff, which flows into lakes or oceans through rivers. The water vapor evaporated from the ocean or land rises and condenses, and falls directly to the ocean or land under the action of gravity.
This phenomenon of continuous transformation, migration and alternation of water is called hydrological cycle. However, the above are only a few sketches of the outline of the global hydrological cycle, and the actual situation of the hydrological cycle is much more complicated. There are traces of hydrological cycle everywhere in the vast space from the atmospheric tropopause about 1 1 km above the ground to the depth of 1 ~ 2 km below the ground.
The atmospheric circulation at different latitudes makes some areas become water vapor sources with evaporation greater than precipitation, while others become water vapor enrichment areas with precipitation greater than evaporation. Inter-basin water transfer projects with different scales can change the path of surface runoff. Every region or water body in the world has its own regional hydrological cycle system, and hydrological cycle systems of various time scales and spatial scales are interrelated and mutually restricted, forming a global hydrological cycle system.
About 577,000 cubic kilometers of water participate in the hydrological cycle every year. The internal cause of hydrological cycle is the physical characteristics that water can be converted into liquid, gas and solid under natural conditions, and the energy driving such a huge hydrological cycle system is the radiation energy of the sun and the potential energy of water in the gravitational field of the earth.
Hydrological cycle is the most important material cycle in nature. It forms clouds, causes rain, affects the climate and ecology of a region, shapes landforms, realizes the migration of geochemical substances, connects global life like a chain, and provides renewable fresh water resources and hydropower resources for human beings. Hydrological cycle makes our planet full of vitality. Without water and hydrological cycle, our planet would be a lifeless and silent desert like the moon.
The existence and movement of water in the circulation process, such as evaporation, precipitation, water level fluctuation in rivers and lakes, ice change, glacier advance and retreat, groundwater movement, water quality change, etc., are collectively referred to as hydrological phenomena. Under the influence of various natural factors and human activities, hydrological phenomena are very complicated in spatial distribution or temporal change.
The time change process of hydrological phenomena is periodic and non-repetitive, which is generally called "quasi-periodic". For example, the water level in a tidal estuary has a daily variation with a period of half or one lunar day; Rivers have a flood season with abundant water and a dry season with little water every year; Through long-term observation, it can be seen that the water quantity of rivers and lakes alternates between continuous wet years and continuous dry years, showing multi-year changes.
The basic reasons for this periodic change are the revolution and rotation of the earth, the relative movement of the earth and the moon and the influence of solar activities, such as the periodic movement of sunspots. They lead to the change of solar radiation and the alternation of seasons, so that hydrological phenomena also have corresponding periodic changes. Of course, hydrological phenomena are also influenced by many other factors, which themselves are constantly changing in time and interact with each other.
A brief history of hydrology
The exploration history of eliminating floods and building water conservancy is as long as the history of human civilization. In production practice, especially in the struggle against floods and droughts, human beings constantly observe various hydrological phenomena, think and study their laws, accumulate rich knowledge about water, and gradually form and develop hydrological science.
Hydrology has a long history, experienced a long gestation period, and developed rapidly in the last century. Similar to many disciplines of natural science, it is still difficult for people to find recognized milestones and divide the historical process of hydrological science into several clear stages. We just follow its footsteps, which can be roughly divided into the following categories.
Germination period (from ancient times to about AD 1400)
In the remains of the cradles of ancient cultures such as the Nile, the Euphrates, the Ganges and the Yellow River, we can see that primitive hydrological observation began in this period. The earliest water level observations were made in China and Egypt.
In the 22nd century BC, Dayu, a legendary master of water control in China, published trees along the mountain to observe the fluctuation of the river. Since then, during the Warring States period, Li Bing's Dujiangyan "Stone Man", Sui Dynasty's water stone carving, Song Dynasty's water monument and so on. It shows that water level observation has been continuously improved.
The earliest rainfall observation first appeared in India in the 4th century BC, and China began to have a rain reporting system in the Qin Dynasty in the 3rd century BC. By A.D. 1247, with more scientific rain gauge and calculation method of rainfall depth, we began to calculate the snowfall depth on the flat land with "bamboo cage snow inspection". In the Ming Dynasty, Liu Tianhe used a hand-made "sand-riding water meter" to measure the sediment volume of the Yellow River.
China's ancient book "Lu Chunqiu" wrote: "The clouds and gas are so sudden that winter and summer are endless; Water springs flow eastward, day and night, inexhaustible, unsatisfied, small as big, heavy as light, national highway. " A simple concept of hydrological cycle is put forward. The Water Mirror Notes, written in the early 6th century A.D., described the general situation of 65,438+0,252 rivers in China at that time, and became a pioneer in hydrogeological investigation.
It is true that these primitive hydrological observations and knowledge are superficial and sporadic, but they have provided important hydrological data for life and production at that time. For example, determining the tax amount according to the amount of rainfall and transmitting water information to the downstream according to the upstream water level all indicate the germination of hydrological science.
Foundation laying period (about 1400 ~ 1900)
The liberation of scientific thought and the progress of science and technology brought by the European Renaissance laid the foundation for the development of hydrology as an independent discipline. During this period, the invention of hydrological instruments made hydrological observation enter the stage of scientific quantitative observation.
1663, Ryan and Hook invented the tipping bucket self-recording rain gauge; 1687, Harley invented the evaporator for measuring the evaporation on the water surface; 1870, Ellis invented the paddle current meter; 1885, Price invented the rotating cup current meter. These modern hydrological instruments make the observation of flow, velocity, evaporation and precipitation reach a considerable accuracy, and various hydrological stations using these modern hydrological instruments for hydrological observation have appeared one after another.
1746, China established the first conventional water level station in the old dam mouth of the Yellow River, and began to systematically observe the water level and report the flood season. These achievements have broadened the observation field of hydrological phenomena in depth and breadth, and created conditions for the theoretical development of hydrological science.
During this period, modern hydrological science theory began to take shape gradually. 1674, Perot put forward the concept of water balance, which became one of the most basic principles of hydrological science. Bernoulli and his son published the energy equation of water flow in 1738, and Xie Cai published the formula of uniform flow in open channel in 1775. Dalton's formula for studying water surface evaporation was established in 1802. 1856 Darcy published Darcy's law describing the movement of groundwater in porous media; 185 1 year, Mowani put forward the concepts of confluence and runoff coefficient, and published the famous reasoning formula for calculating the maximum discharge.
The establishment of these scientific theories has laid a theoretical foundation for the development of hydrology in the fields of river flow, evaporation, groundwater movement, runoff formation and hydrological cycle, indicating that human understanding of hydrological phenomena has developed from superficial and sporadic knowledge in the primary stage to more profound and systematic knowledge. At the same time, it also shows that human exploration of the movement and change law of water on the earth has developed into hypothesis, deduction and reasoning based on a large number of observed facts, and then modern scientific methodology of various theoretical systems has been established.
At the end of 19, specialized hydrological research institutions began to appear, and some countries began to publish hydrological yearbooks. Hydrological monographs, such as Fries's Hydrological Test of Rivers, Faurel's Biography of Lakes, and Edm Edme Mariotte's The Movement of Water, have been published one after another. These works summed up the achievements of hydrological observation and theoretical research at that time, which marked that hydrological science laid the foundation as a modern science.
The rising period of applied hydrology (about 1900 ~ 1950)
During this period, hydrological science has made new achievements in observation methods, theoretical systems and research fields, but the most important progress is the rise of applied hydrology.
In the 20th century, especially after the First World War, a large number of flood control, irrigation, traffic engineering, agriculture, forestry and even urban construction emerged, which put forward more and more new topics for hydrological science. The methods to solve these topics were gradually theorized and systematized from experience and piecemeal, and the application characteristics of hydrological science gradually emerged.
First of all, from 19 14 to 1924, through the work of Heizeng and Foster, the theory and method of probability theory and mathematical statistics are systematically introduced into hydrological science, so that hydrological variables (such as flood peak and flood volume) are related to their probabilities, which opens the way for predicting the hydrological conditions that may occur in the future operation period of the project.
Then from 1932 to 1938, Sherman, Horton, McCarthy, Snyder and others made groundbreaking progress in the calculation of runoff yield and confluence, and opened up a way to calculate flood according to rainfall. Subsequently, Clark, Lindsley and others developed and enriched the above contents on the theories and methods of unit hydrograph, joint analysis of multiple hydrological variables and runoff regulation.
During this period, the hydrological station developed into a large-scale hydrological station network system in the world. These achievements laid the foundation for the rise of applied hydrology in theory, method and data conditions, and took the lead in forming its most important branch discipline-engineering hydrology. Then, agricultural hydrology, forest hydrology and urban hydrology also rose one after another.
From 65438 to 0949, Lin Slay co-authored Applied Hydrology with Kohler and Paul Hess; In the same year, Principles of Applied Hydrology, co-authored by Johnston and Chris, and Handbook of Hydrology compiled by American Society of Civil Engineers came out one after another, summarizing the achievements of this period and marking the birth of applied hydrology. Applied hydrology, characterized by providing various services for production and life directly, has developed rapidly and become the most dynamic branch of modern hydrological science system.
Modern hydrology
Since 1950s, the scale of social production has expanded unprecedentedly, science and technology have entered a new period of development, and a new technological revolution is emerging. The ability of human beings to transform nature has been rapidly enhanced, and the relationship between man and water has changed from a low level in ancient times to a high level in modern times. This new stage endows hydrological science with new impetus and new characteristics.
First of all, due to the outstanding demand of human beings for water resources, the research field of hydrological science is developing in the direction of optimal development and utilization of water resources, providing scientific basis for objective evaluation, rational development, full utilization and protection of water resources;
Second, large-scale human activities are having many impacts on natural water bodies and natural environment. Studying and evaluating the hydrological effect of human activities and the environmental significance of this effect, revealing the laws of hydrological phenomena under the influence of human activities, and then exploring new methods and new ways of hydrological analysis to prevent the influence of human activities on hydrological cycle from developing in a direction that is not conducive to the living environment of human beings, are all becoming new topics facing hydrological science.
In addition, modern science and technology have also made great progress in the means of obtaining hydrological information and the methods of analyzing hydrological information. For example, the application of remote sensing technology makes it possible to observe large-scale macro-hydrological phenomena at the same time; The application of nuclear technology enables people to obtain microscopic hydrological information; Hydrological simulation method, hydrological stochastic analysis method and hydrological system analysis method make people's ability to study hydrological phenomena develop to a new level; Especially, the application of computer makes hydrology science develop from hydrological observation to the study of basic laws, from manual and mechanical operation to automation with computer as the core.
The marginal science between hydrological science and other sciences is constantly rising, and the gap between disciplines is gradually filled. At the same time, people began to see that water has become an important factor affecting social development. While water shows its natural attributes, its social attributes are increasingly prominent and gradually recognized by people. Therefore, hydrological science will probably develop into a comprehensive science with the dual nature of natural science and social science.
Research characteristics of hydrology
Hydrological cycle is the existence conditions of various water bodies in nature and their relations. It is the sum of various movements and changes of water, and it is the main object and core content of hydrological science research. In the process of hydrological cycle, the characteristics of hydrological phenomena determine the characteristics of hydrological science research.
First of all, hydrological science regards all kinds of hydrological phenomena as a whole, and studies the influence of atmosphere, lithosphere, biosphere and human activities. For example, when the water consumption balance method is used to study the change of water quantity in the basin, not only the water vapor transport in the atmosphere around the basin, but also the change of water content in the atmosphere above the basin should be considered; Both precipitation and evaporation should be considered; We should not only consider the surface runoff of the basin, but also consider the exchange of soil water content and groundwater inside and outside the basin, and also consider the influence of water conservancy projects and other human activities in the basin.
Secondly, hydrological science mainly predicts or predicts the future situation of hydrological situation according to the existing hydrological data, and directly serves human life and production. For example, it provides flood forecast and various water regime forecasts, makes medium-and long-term predictions on the occurrence of drought and flood disasters, and makes probability predictions on the catastrophic floods that may be encountered in the future operation period of water conservancy projects.
Hydrological science mainly relies on the establishment of a network of hydrological observation stations from local to global to analyze and study hydrological phenomena occurring in nature. All kinds of hydrological experiments, except a few in the laboratory, are mainly carried out in nature, such as experimental basins.
Genetic analysis and statistical analysis are widely used in hydrological science research, and they are combined as much as possible. Genetic analysis is mainly based on physical principles, and usually some form of deterministic model is established to study the deterministic laws in the development and evolution of hydrological phenomena. Statistical analysis is usually based on probability theory, and a probability model (pure stochastic model) is established to explore the statistical law of hydrological phenomena.
The branch of hydrological science.
Because of the important role of water in human survival and social development, hydrology is not only a basic science, but also an applied science that widely serves production and life.
Hydrological science constantly draws nutrition from basic sciences such as mathematics, physics and chemistry. It uses the laws and methods of mathematical mechanics to describe the movement of water; Using the principles of heat, acoustics and optics in physics, the thermal state of water body is studied and the acoustic and optical phenomena in water body are explained. According to the theory of chemical bond and molecular association, the reasons and ways of liquid, gas and solid water transformation are expounded.
Because hydrological cycle closely links hydrosphere, atmosphere and lithosphere, hydrological science is closely related to atmospheric science, geology and physical geography in the earth science system.
Hydrological science began to mainly study rivers, lakes, swamps, glaciers and snow, and later expanded to groundwater, water in the atmosphere and water in the ocean. Traditional hydrology is divided into branches according to the research objects, mainly including river hydrology, lake hydrology, swamp hydrology, glacier hydrology, snow water literature, hydrometeorology, groundwater hydrology, regional hydrology and seawater literature.
River hydrology, also known as river hydrology, studies the physical and geographical characteristics of rivers, the recharge of rivers, the formation and change of runoff, the water temperature and ice conditions of rivers, the evolution of sediment transport in rivers and riverbeds, the chemical composition of rivers and the relationship between rivers and the environment.
Lake hydrology mainly studies the change and movement of water quantity in lakes, the physical characteristics and chemical composition of lake water, and the utilization of lake sediments.
Marsh hydrology studies the physical and chemical properties of marsh runoff, marsh water, marsh recharge to rivers and lakes, and marsh improvement.
Glacier hydrology mainly studies the distribution, formation and movement of glaciers, the formation process and temporal and spatial distribution of glacial meltwater runoff, the formation mechanism and prediction of sudden flood of glaciers, and the utilization of glacier water resources.
Snow-water literature mainly studies the quantity and distribution of snow, the process of snow melting, the supply of snow-melting water to rivers and lakes, the formation and prediction of snow-melting flood, and sometimes it is called snow-ice water literature together with glacier hydrology.
Hydrometeorology studies the relationship between hydrosphere and atmosphere, including hydrological cycle and water balance in the atmosphere, and water exchange between the atmosphere and the underlying surface with evaporation, condensation and precipitation as the main ways, paying special attention to the occurrence and development of rainstorm and drought.
Groundwater hydrology mainly studies the formation and movement of groundwater, the mutual replenishment of groundwater and rivers and lakes, the evaluation and development and utilization of groundwater resources.
Regional hydrology focuses on hydrological phenomena in some specific areas, such as estuary hydrology, slope hydrology, plain hydrology, karst hydrology, arid hydrology and so on.
Marine water literature focuses on the physical properties and chemical composition of marine water, waves, tides, ocean currents, coastal sediment movement and so on. These disciplines are often called general hydrology or hydrology.
Hydrological science mainly obtains the information of temporal and spatial distribution and movement change of water body through fixed-point observation, field investigation and hydrological experiment (mainly field experiment), and gradually forms three branches of hydrological measurement, hydrological investigation and hydrological experiment.
Hydrological test studies how to measure the quantity of various hydrological elements correctly, economically and quickly and their changes in time and space, mainly including the study of station network layout, test method and data reorganization method. It also includes the development of measuring instruments and the research of data storage, retrieval and transmission systems.
Hydrological investigation is a part of the field investigation and investigation of hydrological science, which aims to make a scientific analysis and evaluation of the shape and quantity of water bodies and natural geographical conditions in the catchment area. In China, the investigation of historical rainstorm, historical flood and low water is an important part of hydrological investigation.
Hydrological experiment aims to reveal some laws of water movement and change in each link of hydrological cycle through field and indoor experiments, such as laws of water infiltration into soil, laws of soil water movement, laws of runoff formation, laws of soil and water surface evaporation, hydrological effects of human activities, etc.
Hydrology, as an applied science, mainly includes engineering hydrology, agricultural hydrology, forest hydrology, urban hydrology, medical (health) hydrology and other sub-disciplines, among which engineering hydrology has developed most rapidly.
Engineering hydrology includes hydrological calculation, hydraulic calculation, hydrological forecast and other components. Hydrological calculation and hydraulic calculation provide hydrological basis for the planning and design of various flood control projects, irrigation projects, hydropower projects, shipping projects, road and bridge crossing projects and military projects.
Hydrological forecasting provides various forms of hydrological forecasting such as flood, low water and ice conditions for engineering construction and operation and various departments of national economy.
Agricultural hydrology mainly studies the hydrological problems related to crop growth in water-soil-plant system, especially paying attention to the laws of plant discharge and soil moisture movement, and providing hydrological basis for agricultural planning and crop yield increase.
Forest hydrology focuses on the role of forest in hydrological cycle, that is, the hydrological effect of forest, including the influence of forest on precipitation, evaporation and runoff formation.
Urban hydrology is a relatively young branch of applied hydrology, which mainly studies the water resources in urban development, the environmental impact of market drainage and the impact of cities on runoff formation.
Since 1950s, with the rapid development of science and technology, hydrological science has introduced many new achievements from other disciplines, and some new branches have emerged. For example, in hydrological investigation and hydrological forecast, remote sensing hydrology has been gradually formed by studying the application of remote sensing technology; The application of nuclear technology in hydrological experiments and groundwater movement research has gradually formed isotope hydrology; With the introduction of stochastic process theory and method, stochastic hydrology has gradually formed.
Although these new branches cannot be compared with the original disciplines in the hydrological science system in terms of maturity, they show that hydrological science continues to cultivate and sprout new branches.